The invention relates to a 6-high cold rolling mills having side supported work rolls of the kind described generally in U.S. Pat. Nos. 4,270,370 and 4,531,394. The improvements described herein are of particular use when the rolling mill is part of a continuous line described generally in U.S. Pat. No. 5,197,179 or is of the kind described in U.S. Pat. No. 6,041,036 or when the mill is supplied as a tandem mill, incorporating several mill stands rolling metal strip in a fixed direction.
It is well known in the art that during rolling, drive torque must be delivered to the work rolls. Since the work rolls in such mills are free floating and thus are not driven, the torque must be delivered in the form of a tangential force which acts in a horizontal direction at the contact line between each work roll and its main support roll (the intermediate roll). The same is true regardless of whether the intermediate rolls or the back-up rolls are driven. This force always pushes each work roll towards the entry side of the mill and the reaction force pushes the adjacent intermediate roll towards the exit side of the mill.
These mills are supplied with a side support structure at each side of each work roll, each cluster comprising one side support roll which is nested between two rows of side support caster bearings, each row mounted upon a shaft with the shaft being supported by saddles mounted on a cluster arm, with the cluster arm being supported in its turn by a side support beam adjustably mounted between drive and operator side mill housings.
This structure is suitable for a reversing mill where, depending upon rolling direction either the left side or the right side support structures may be loaded by the tangential torque forces. However, for a non-reversing mill, it might be thought that there would be no need for side support structures at the exit side of the mill since such structures would not be subjected to load during rolling. In fact, the exit side support structure is needed for several reasons. Firstly, it is needed to ensure that the work rolls can be set in the correct position abutting the entry side support roll before rolling commences. Secondly, it is needed because sometimes in order to reduce the horizontal forces acting on the entry side support caster bearings and on the intermediate roll neck bearings, it is desirable to operate such mills with the work rolls off-set towards the exit side so that a horizontal component of the roll separating force will develop which will act to push the work rolls towards the exit side and the intermediate rolls towards the entry side, thus off-setting the torque reaction forces. Under some conditions, for example when initially screwing down to set the roll gap with the mill stationary, the torque reaction forces will be zero, but the horizontal component of roll separating force will be non-zero and there will be a net force acting to push the work rolls towards the exit side, thus necessitating exit side support structures.
To control the flatness of the strip rolled on such a mill, two methods exist in the art. These are axial shifting of the intermediate rolls, and bending of the intermediate rolls. These methods are quite effective for controlling second order flatness defects such as center-buckle and wavy edge, but are not able to correct more local defects such as non-symmetrical quarter buckle and localized strip buckle.
By contrast, non side-supported mills such as 4hi mills and conventional 6-high mills not only incorporate work roll and intermediate roll bending, and (6-high only) intermediate roll shifting, but also incorporate multi-zone work roll cooling sprays which are able to achieve localized correction of flatness defects by controlling work roll temperature distribution. At each zone there are usually 3 spray nozzles with respective flow areas in the ration 1:2:4, each nozzle being controlled by solenoid valve. Depending upon which solenoid valves are on, the flow to each zone can be adjusted with a turn-down ratio of 1:7. As the work roll diameter on such mills is relatively large, it's easily possible to fit such a coolant spray system into the mill structure adjacent to the work rolls.
On prior art side supported 6-high mills, not only is the work roll diameter relatively small, but the space at each side of the work rolls is filled with the side support structure and there is no room to mount work roll cooling sprays.
The objective of this invention is to provide for a side supported 6-high mill a novel side support structure, which will incorporate multi-zone work roll cooling sprays.
Reference will now be made in detail to an embodiment of the invention, an example of which is illustrated in the accompanying drawings.